The major objective of this communication is to evaluate procedures for estimation of the isosteric heat of adsorption, Q(st), in microporous materials such as zeolites, metal organic frameworks (MOFs), and zeolitic imidazolate frameworks (ZIFs). For this purpose we have carefully analyzed published experimental data on adsorption isotherms at different temperatures, I,. for a variety of guest molecules (water, methanol, ethanol, dimethylether, cyclohexane, benzene, toluene, xylene, ethylbenzene, ethyne, propene, propane, iso-butane, 1-butene, n-hexane) in several zeolites, MOFs, and ZIFs. Our analysis shows that when the binding energy with the structural framework is dominated by molecule-molecule interaction forces, Q(st) approximate to Delta H-vap, the molar enthalpy of vaporization. In such cases, the molar loading q(i) at any temperature T and pressure p(i), is a unique function of (p(i)/P-i(sat)) where P-i(sat) is the saturated vapor pressure at T. For most guest/host combinations, however, the Q(st), values are significantly higher than Delta H-vap because of strong interactions of guest molecules with the material framework. For several guest/host combinations, a reasonable estimation of Q(st) values is obtained by addition of the Toth potential to Delta H-vap. (C) 2014 Elsevier Ltd. All rights reserved.